Fix test failures and add MotherDuck apply_database_override

- Add apply_database_override to MotherDuck adapter (was missing despite
  supports_multiple_databases=True)
- Fix test_explorer_refresh_cursor to update store.connections instead
  of app.connections directly
- Add missing _load_folder_async and _load_columns_async to MockHost
- Fix MockTreeNode.add() to track parent references for tree traversal

Author: Maxteabag

sqlit/domains/connections/providers/motherduck/adapter.py

@@ -28,6 +28,12 @@ def supports_multiple_databases(self) -> bool:
         """MotherDuck supports multiple databases."""
         return True
 
+    def apply_database_override(self, config: ConnectionConfig, database: str) -> ConnectionConfig:
+        """Apply a default database for unqualified queries."""
+        if not database:
+            return config
+        return config.with_endpoint(database=database)
+
     def connect(self, config: ConnectionConfig) -> Any:
         """Connect to MotherDuck cloud database."""
         duckdb = self._import_driver_module(

tests/integration/test_explorer_refresh_cursor.py

@@ -74,7 +74,8 @@ async def test_explorer_refresh_keeps_cursor_on_connection() -> None:
 
         # Simulate refresh with a reordered connection list (e.g. discovery/sort changes).
         # Keep the selected connection in the middle so a jump to first/last fails.
-        app.connections = [connections[2], connections[1], connections[0]]
+        # Update the store so refresh picks up the new order.
+        app.services.connection_store.connections = [connections[2], connections[1], connections[0]]
 
         before_token = getattr(app, "_tree_refresh_token", None)
         await pilot.press("f")
@@ -143,7 +144,8 @@ async def test_explorer_refresh_keeps_cursor_when_connection_moves_folder() -> N
         assert app.object_tree.cursor_node == target
 
         # Move the selected connection to a different folder before refresh.
-        app.connections = [
+        # Update the store so refresh picks up the new folder assignments.
+        app.services.connection_store.connections = [
             ConnectionConfig(
                 name="Alpha",
                 db_type="sqlite",
@@ -177,4 +179,3 @@ async def test_explorer_refresh_keeps_cursor_when_connection_moves_folder() -> N
         parent = getattr(cursor, "parent", None)
         parent_data = getattr(parent, "data", None)
         assert getattr(parent_data, "name", None) == "B"
-

tests/ui/explorer/test_refresh_cursor_restore.py

@@ -202,6 +202,14 @@ def batch_update(self):
     def notify(self, message, severity="info"):
         pass
 
+    def _load_folder_async(self, node, data):
+        """No-op for testing - folder loading is simulated manually."""
+        pass
+
+    def _load_columns_async(self, node, data):
+        """No-op for testing - column loading is simulated manually."""
+        pass
+
 
 @dataclass
 class MockColumn:

tests/ui/test_tree_schema_grouping.py

@@ -40,20 +40,25 @@ def format_table_name(self, schema: str, name: str) -> str:
 class MockTreeNode:
     """Mock tree node for testing."""
 
-    def __init__(self, label: str = "", data: tuple = None):
+    def __init__(self, label: str = "", data: tuple = None, parent: "MockTreeNode | None" = None):
         self.label = label
         self.data = data
+        self.parent = parent
         self.children: list[MockTreeNode] = []
         self.allow_expand = False
+        self.is_expanded = False
 
-    def add(self, label: str) -> MockTreeNode:
-        child = MockTreeNode(label)
+    def add(self, label: str) -> "MockTreeNode":
+        child = MockTreeNode(label, parent=self)
         self.children.append(child)
         return child
 
-    def add_leaf(self, label: str) -> MockTreeNode:
+    def add_leaf(self, label: str) -> "MockTreeNode":
         return self.add(label)
 
+    def expand(self) -> None:
+        self.is_expanded = True
+
 
 class TestSchemaGrouping:
     """Test that tables are grouped by schema correctly."""